CHARACTERIZATION OF THE ROLE OF dRanBPM, dfmr1 AND THE MUSHROOM BODY DURING LARVAL LOCOMOTION IN DROSOPHILA

Abstract

<p>Wild-type <em>Drosophila</em> larvae display photophobic behaviour when confronted with a light stimulus. This behaviour is mediated by changes in larval locomotion including increased direction change and pausing in addition to decreased contraction frequency. Foraging third instar larvae that are homozygous mutant for the <em>Drosophila Ran Binding Protein in the Microtubule Organizing Center (dRanBPM) </em>gene exhibit a reduced response to light and two alleles display a severe locomotion deficit. <em>dRanBPM</em> functional domains show a considerable number of identical amino acids when compared with orthologous genes. The human orthologue RanBPM binds to Fragile X Mental Retardation Protein (FMRP), a protein for which the loss of expression causes Fragile X syndrome. Wandering <em>Drosophila fragile</em> X mental retardation 1 (dfmr1) mutant larvae show increased direction change and reduced time spent in linear locomotion in a dark assay. Double mutant larvae homozygous for a <em>dfmr1</em> mutant allele and carrying one copy of a <em>dRanBPM</em> mutant allele were tested for turning and response to light phenotypes. The results presented here indicate that <em>dRanBPM</em> and <em>dfmr1</em> act independently to modulate aspects of larval locomotion. Expression of dRanBPM is found in distinct sets of neurons in the larval CNS including the mushroom bodies (MBs). Neuronal silencing of the MBs in foraging third instar larvae resulted in a reduction in response to light. Finally, this reduction in response to light stimuli was characterized as a decrease in mean direction change during the light.</p>